In the conventional motor vehicle body construction, a vertically oriented center pillar is provided for joining a roof stringer to a lower lengthwise member of the vehicle, such as, for example, a floor sill member. Since the center pillar takes the brunt of the force impact experienced in a side collision, it is desirable to configure the center pillar with an enclosed cross section for rigidity and contoured connecting end portions for better transfer of energy and force distribution from the center pillar to the adjoining lengthwise members of the vehicle.
Conventional center pillar constructions having smoothly curving transitional end portions fabricated from sheet metal stampings are known in the prior art. For example, German patent document DE-0S 21 64 705 discloses a curved transition between a center pillar to a lengthwise bottom door sill member made from pieces of sheet metal.
German patent document DE-GM 87 17 616 discloses another solution wherein a section is made from a single sheet metal piece. This patent document describes a door frame in a utility vehicle, whereby the section forming a vertical center pillar member is split at its lower end region where it joins a horizontal member and one of the two resulting split terminal end regions is molded for flush connection to the horizontal frame member. A disadvantage with this type of connection is that split reduces the strength of the connection, especially if a segment is removed thereby, as in the example according to DE-GM 87 17 616. Further, the split connection according to this process requires additional labor expense.
A recent trend in the design and fabrication motor vehicle bodies has seen a shift away from the reliance on sheet metal as a primary construction material for many frame elements in favor of frame elements formed from extruded light metal alloys in view of the advantages of weight reduction and ease of implementation in the manufacturing process afforded by the new materials. For example, extruded light metal center pillars for joining a roof stringer to a floor sill member are well known in the art. However, in view of the limitations associated with the extrusion process, a center pillar formed from as an extrusion typically has only a uniform cross section from top end to bottom end. This poses a problem where it is desirable to selectively vary the cross-sectional dimension of center pillar for additional rigidity where it is needed most. Further, in the case of an extruded light metal center pillar construction, it is difficult to incorporate smoothly curving transition end regions to smoothly transfer force and energy to adjoining frame members.
Accordingly, there is a definite need in the art for a center pillar construction formed from extruded light metals which is of low cost to implement in the manufacture process of a motor vehicle body and which provides good force transfer characteristics to adjacently connected frame members and which also increases the overall rigidity of the vehicle frame.